Ion implantation is a process of introducing dopants or impurities into a substrate via bombardment. In semiconductor manufacturing, the dopants are introduced to alter electrical, optical, or mechanical properties. For example, dopants may be introduced into an intrinsic semiconductor substrate to alter the type and level of conductivity of the substrate. In manufacturing an integrated circuit (IC), a precise doping profile provides improved IC performance. To achieve a desired doping profile, one or more dopants may be implanted in the form of ions in various doses and various energy levels.
Ion implantation systems may comprise an ion source and a series of beam-line components. The ion source may comprise a chamber where desired ions are generated. The ion source may also comprise a power source and an extraction electrode assembly disposed near the chamber. The beam-line components may include, for example, a mass analyzer, a first acceleration or deceleration stage, a collimator, and a second acceleration or deceleration stage. Much like a series of optical lenses for manipulating a light beam, the beam-line components can filter, focus, and manipulate ions or ion beam having desired species, shape, energy, and other qualities. The ion beam passes through the beam-line components and may be directed toward a substrate or wafer mounted on a platen or clamp. The substrate may be moved in one or more dimensions (e.g., translate, rotate, and tilt) by an apparatus, sometimes referred to as a roplat.
The ion implanter generates a stable, well-defined ion beam for a variety of different ion species and extraction voltages. After several hours of operation using source gases (such as AsH3, PH3, BF3, and other species), beam constituents eventually create deposits on the beam optics. Beam optics within a line-of-sight of the wafer also become coated with residues from the wafer, including Si and photoresist compounds. These residues build up on the beam-line components, causing spikes in the DC potentials during operation (e.g., in the case of electrically biased components). Eventually the residues flake off, causing an increased likelihood of particulate contamination on the wafer.
One way to prevent the effect of the material accumulation is to intermittently replace beam-line components of the ion implanter system. Alternatively, beam-line components may be manually cleaned, including powering down the ion source, and releasing the vacuum within the system. After replacing or cleaning the beam-line components, the system is then evacuated and powered to reach an operational condition. Accordingly, these maintenance processes may be time consuming. In addition, the beam-line component is not used during the maintenance processes. As such, frequent maintenance processes may decrease the time available for IC production, thus increasing overall manufacturing cost.